Method And Arrangement For Measuring Transmission Quality In A Packet Mode Communication Network

ABSTRACT

A method and an arrangement for measuring a transmission quality in terms of lost packets between two pre-determined nodes arranged to transmit and receive packets in a packet mode communication network. Each node is provided with a counter arranged to count transmitted packets in one node and received packets in the other node during a pre-determined period of time. After the pre-determined period of time has ended, the counters are compared in order to obtain a packet loss measurement.

TECHNICAL FIELD

The present invention relates to the field of packet mode communicationnetworks and, particularly, to an arrangement allowing for measuring thetransmission quality in terms of lost packets in a packet modecommunication network as well as a method for such measuring.

BACKGROUND OF THE INVENTION

Packet mode communication networks transmit information/data in the formof packets. One example of such a network is the Internet network whichis operated with IP protocol (Internet protocol). IP is used fortransmitting data from higher-level protocols, such as TCP and UDP, inIP packets from one host to another host in the network. Each packet ishandled independent of other packets and each packet may reach thedestination through different network routes. The communicationservices, such as voice/sound or visual communications, require acertain level of quality across the IP network.

One prior art approach of determining quality for packetized informationis shown in WO 2005/004370, which discloses a method for near real timeanalysis which samples packets from a stream of IP packets thatrepresent a communication session between a pair of endpoints anddetermines two metrics from the sampled packets, quantity of lostpackets and packet timing. The packet loss is calculated by looking atthe RTP sequence number in each packet. Gaps in the sequence representlost packets and the packet loss is calculated as the number of lostpackets divided by the sum of received packets plus lost packets.

However, this prior art approach measures the quality of the network ina complicated manner involving several metrics to consider.Additionally, protocols like RTP require large headers of the packets,typically 12 octets for the RTP protocol, which is capacity consuming.Other existing solutions in this area involve hardware (HW) that iscostly.

There is, thus, today no cheap, easy way for two peer endpoints of an IPtransmission network to know the overall transmission quality of theintermediary IP network connecting them.

SUMMARY OF THE INVENTION

Accordingly, it is an objective with the present invention to provide animproved method for measuring a transmission quality in terms of lostpackets between two pre-determined nodes arranged to transmit andreceive packets in a packet mode communication network.

This objective is achieved through a method of providing each node witha counter whereby each node is able to reset the counter on the othernode, counting transmitted packets in one node and received packets inthe other node during a pre-determined period of time and, comparing thecounters after the pre-determined period of time has ended in order toobtain a packet loss measurement.

Another objective with the present invention is to provide an improvedarrangement for measuring a transmission quality in terms of lostpackets between two pre-determined nodes arranged to transmit andreceive packets in a packet mode communication network.

This other objective is achieved through providing an arrangementcomprising a counter in each node arranged to count transmitted packetsin one node and received packets in the other node during apre-determined period of time, where each node is arranged to be able toreset the counter on the other node and, means for comparing thecounters after the pre-determined period of time has ended in order toobtain a packet loss measurement.

One advantage with the present invention is the possibility to identify,in a relatively easy manner, weaknesses in an intermediary IP networkthat effects the performance of end user applications. Another advantageis the possibility to dimension the intermediary IP network such, thatit shall not be a bottleneck.

Still other objects and features of the present invention will becomeapparent from the following detailed description considered inconjunction with the accompanying drawings. It is to be understood,however, that the drawings are designed solely for purposes ofillustration and not as a definition of the limits of the invention, forwhich reference should be made to the appended claims. It should befurther understood that the drawings are not necessarily drawn to scaleand that, unless otherwise indicated, they are merely intended toconceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein like reference characters denote similarelements throughout the several views:

FIG. 1 is an exemplary block diagram of a mobile communication network;

FIG. 2 is a block diagram showing an embodiment of the present inventionwhere a terminating side comprises several hardware entities;

FIG. 3 is a flow chart showing the inventive method steps on both anoriginating and a terminating side.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The Global System for Mobile Communication (GSM) is one of the mostwidely deployd communication standards for mobile wirelesscommunication. As an extension of GSM in order to introducepacket-switched technology, General Packet Radio Service (GPRS) wasdeveloped by Third Generation Partnership Project (3GPP). One limitationof GPRS is that it does not support voice services. Therefore, theEuropean Telecommunications Standards Institute (ETSI) has developed anew standard for GSM to support high rate data services. This standardis known as Enhanced Data Rates for Global Evolution (EDGE). Oneobjective of EDGE is to provide voice services over the packet-switchednetwork.

A network according to these standards comprises a core network (CN),radio access networks (RAN) and mobile stations (MS) attached to a RAN,such as the GSM/EDGE Radio Access Network (GERAN) architecture. Thiskind of network is basically an extension of Internet and supports IP inall instances from the mobile station to the core network.

A block diagram of an exemplary 3GPP GSM system network is shown inFIG. 1. The network comprises a radio access network (RAN), which in thepreferred embodiment of the present invention is a GSM/EDGE Radio AccessNetwork (GERAN) 10 and a core network (CN) 20. The GERAN 10 and the CN20 provide communication and control for a plurality of mobile stations(MS) 12.

The GERAN architecture 10 comprises a plurality of Base Station Systems(BSS) 15 each controlled by a Base Station Controller (BSC) 16 which isconnected to a set of Base Transciever Stations (BTS) 18. The BTSs 18comprise the antennas, RF equipment and baseband processing circuitsneeded to communicate with the MSs 12. The BTSs 18 are connected to theBSC 16 through the Abis-interface.

The core network 20 typically comprises at least one Serving GPRSSupport Node (SGSN) 22, one or more Gateway GPRS Support Node (GGSN) 28,at least one mobile switching center (MSC) 24, which may include avisitor location register (VLR) (not shown in FIG. 1), a Gateway MSC(GMSC) 26, and a GPRS home location register (HLR) 25. The CN 20provides both circuit-switched and packet data communication withvarious external networks, typically including the Public SwitchedTelephone Network (PSTN) 32 and one or more packet mode communicationnetwork, such as the Internet 34. The GERAN 10 connects to the CN 20through the A, Gb and Iu interfaces.

In the present invention a test function is added on each side of anintermediary IP network between two nodes in a packet mode communicationnetwork, in order to measure the overall quality of the intermediary IPnetwork. The test function is a duplex function and is able to measurethe quality of the intermediary IP network in both directionsindependently of each other. The quality is measured as the number ofpackets that is lost in the intermediary IP network between the twosides during a pre-determined period of time, i.e. the test period, andthus a counter is provided on each side of the intermediary IP networkto be measured.

The side that is sending the measured IP packets is in this contextcalled the originating side and the side that is receiving the measuredIP packets is called the terminating side. The test function may beinitiated on one or both sides of the intermediary IP network that shallbe measured, but shall always be initiated on the terminating side ofthe measured IP network before it is initiated on the originating side.

The test function arrangement according to the present invention formeasuring a transmission quality in terms of lost packets between twopre-determined nodes arranged to transmit and receive packets in apacket mode communication network, thus comprises:

-   -   a counter in each node arranged to count transmitted packets in        one node and received packets in the other node during a        pre-determined period of time, where each node is arranged to be        able to reset the counter on the other node;    -   means for setting a testbit in each transmitted packet in order        to indicate to the terminating side (receiving node) that the        packet has been counted on the originating side (transmitting        node), whereby the terminating side increases the counter for        each received packet where said testbit is set;    -   means for setting said testbit to zero after the pre-determined        period of time has ended in order to indicate to the terminating        side that the received packet not has been counted on the        originating side;    -   means for comparing the counters after the pre-determined period        of time has ended in order to obtain a packet loss measurement.        The originating side is arranged to fetch the packet received        counter value from the terminating side so, that the counters        from each side of the interface can be compared towards each        other to identify the experienced packet loss. Optionally, the        comparison may either be made manually or, the terminating side        may send a message including the local counter value from the        terminating side to the originating side when packets with said        testbit set to zero have been received for a pre-determined        period of time on the terminating side.

The terminating side may be arranged to forward the received packets toanother node. In order not to pollute the IP network that may be presentafter the terminating side of the test function, the terminating sidehas to set the testbit in the received packet to zero before forwardingthe packet to the other node. In this way, the test function may beinitiated on separate parts of an overall IP network without interferingwith each other's measurement results. If the complete IP network is tobe measured, i.e. if the two nodes to be measured are two endpoints, therouters/switches in the network must be coordinated so that the testfunction is not activated in any of those nodes, i.e. the counters atthe intermediary nodes are deactivated.

The terminating side may comprise several HW entities on which IPpackets may be received, thus making aggregation of sub-local countersnecessary. This is shown in FIG. 2. FIG. 2 shows a Central Processor(CP) 40 comprising the local counter 42 of the terminating side. IPpackets from the remote side are counted in sub-local test counters 44,45 and 46 provided in Regional Processors (RP). The aggregation of thesub-local counters 44, 45 and 46 into the local counter 42 may either bedone in real-time through the test period or after the test period hasended. It is possible to measure the quality of the intermediary IPnetwork to a subset of HW devices each equipped with an IP address, byletting the originating side set the testbit and count only in thosepackets sent to a specific HW entity.

In a preferred embodiment of the present invention, the procedure on theoriginating side for measuring the transmission quality in terms of lostpackets from the originating side provided with a counter to theterminating side provided with a counter during a pre-determined periodof time (test period), shown in FIG. 3 on the right hand side, is asfollows:

-   -   initiating the test function (step 51) by resetting counters in        originating and terminating sides;    -   sending packets to terminating side and increasing the counter        for each packet sent to the terminating side (step 52) and        setting a testbit in each transmitted packet in order to        indicate to the terminating side that the packet has been        counted in the originating side;    -   deactivating the test function by setting the testbit to zero        (step 53) after the pre-determined period of time has ended in        order to indicate to the terminating side that the received        packet not has been counted on the originating side;    -   optionally, fetching the packet received counter value from the        terminating side after the pre-determined period of time has        ended;    -   comparing the counters (step 54) in order to obtain a packet        loss measurement. Alternatively, the comparison is made manually        or the terminating side may send a message including the local        counter value from the terminating side to the originating side        when packets with said testbit set to zero have been received        for a pre-determined period of time on the terminating side.

In a preferred embodiment of the present invention, the procedure on theterminating side for measuring the transmission quality in terms of lostpackets from the originating side to the terminating side during apre-determined period of time (test period), shown in FIG. 3 on the lefthand side, is as follows:

-   -   initiating the test function on request from originating side;    -   receiving packets from the originating side and increasing        counter for all downlink packets (received packets) with testbit        set (step 55);    -   optionally, sending a message including the counter value from        the terminating side to the originating side when packets with        said testbit set to zero have been received for a pre-determined        period of time (not specifically shown in FIG. 3), to enable        comparison of the counters (step 54). Alternatively, the        comparison is made manually or the originating side is arranged        to fetch the packet received counter value from the terminating        side as described above.

A first preferred embodiment of the present invention for measuring thetransmission quality in terms of lost packets between two nodes arrangedto transmit and receive packets in a packet mode communication network,concerns the 3GPP GSM system (shown in FIG. 1) and the Gb-interfacewhich connects a GSM/EDGE Radio Access Network (GERAN) to a core network(CN). There is today no way to know how much data that is lost in theintermediary IP network between the SGSN 22 and the BSS 15, i.e. theGb-interface. Each side of the Gb-interface may very well consist of anumber of HW entities all equipped with an IP address, between whichthere is full mesh connectivity, which complicates the problem withmeasuring the overall quality of the intermediary IP network on theapplication layer, which is the Network Service (NS) layer.

In the first preferred embodiment of the present invention, a NetworkService (NS) entity may decide to measure the packet loss in theintermediary IP network, operated with IP protocol, towards its peerentity. It can do so between one or more of its local endpoints towardsone or more of its remote IP endpoints. Each local IP endpointimplements a Packet Sent Counter and each remote IP endpoint implementsa Packet Received Counter and these counters are used for comparisonafter the test period has ended in accordance with the presentinvention.

The IP Endpoint Information Reset procedure is used to initiate thepacket loss measurement function in the remote peer NS entity, i.e. thePacket Received Counter of all indicated local IP endpoints configuredin the peer NS entity are reset. Optionally, all local IP endpoints arereset, not only the indicated local IP endpoints. When the packet lossmeasurement function has been initiated in the remote peer NS entity,the Packet Received Count bit is set to “request counting” in all NSProtocol Data Units (NS-PDUs) sent to the IP endpoints of the remotepeer NS entity that are to be measured. Before sending an NS-PDU to suchan IP endpoint, the sending side shall increase its Packet Sent Counterfor the sending IP endpoint. At the receiving NS entity, the PacketReceived Counter is increased for every received NS-PDU where the PacketReceived Count bit is set to “request counting”.

After a completed test period, the packet loss measurement function isswitched off, meaning that the Packet Received Count bit is set to “nocounting” in all NS-PDUs sent to the remote peer NS entity. At thereceiving NS entity, the Packet Received Counter is not increased whenan NS-PDU is received where the Packet Received Count bit is set to “nocounting”. The Packet Received Counters from the peer NS entity arefetched with the IP Endpoint Information procedure. The actual packetloss experienced during a test period is found through comparing thePacket Sent/Received Counters from each side of the interface.

In a second preferred embodiment of the present invention, the inventivemethod for measuring the transmission quality in terms of lost packetsis implemented in the Abis-interface, i.e between the BTSs 18 and theBSC 16.

In a third preferred embodiment of the present invention, the inventivemethod for measuring the transmission quality in terms of lost packetsis implemented in the Iu-interface, between the SGSN 22 and a RadioNetwork Controller (RNC) which is used in a Universal Terrestrial RAN(UTRAN) architecture.

In a fourth preferred embodiment of the present invention, the inventivemethod for measuring the transmission quality in terms of lost packetsis implemented in the A-interface, i.e. between the MSC 24 and the BSS15.

Thus, while there have been shown and described and pointed outfundamental novel features of the invention as applied to a preferredembodiment thereof, it will be understood that various omissions andsubstitutions and changes in the form and details of the devicesillustrated, and in their operation, may be made by those skilled in theart without departing from the spirit of the invention. For example, itis expressly intended that all combinations of those elements and/ormethod steps which perform substantially the same function insubstantially the same way to achieve the same results are within thescope of the invention. Moreover, it should be recognized thatstructures and/or elements and/or method steps shown and/or described inconnection with any disclosed form or embodiment of the invention may beincorporated in any other disclosed or described or suggested form orembodiment as a general matter of design choice. It is the intention,therefore, to be limited only as indicated by the scope of the claimsappended hereto.

1. A method for measuring a transmission quality in terms of lostpackets between two pre-determined nodes arranged to transmit andreceive packets in a packet mode communication network, said methodcomprising the steps of: providing each node with a counter, wherebyeach node is able to reset the counter on the other node; countingtransmitted packets in one node and received packets in the other nodeduring a pre-determined period of time; and, comparing the countersafter the pre-determined period of time has ended in order to obtain apacket loss measurement.
 2. The method according to claim 1, wherein thestep of counting comprises the steps of: setting a testbit in eachtransmitted packet in order to indicate to the receiving node that thepacket has been counted in the transmitting node, whereby the receivingnode increases the counter for each received packet where said testbitis set; and, setting said testbit to zero after the pre-determinedperiod of time has ended in order to indicate to the receiving node thatthe received packet not has been counted on the transmitting node. 3.The method according to claim 1, wherein the step of comparing comprisesthe step of fetching the counter value from the receiving node to thetransmitting node.
 4. The method according to claim 2, wherein the stepof comparing comprises the step of sending a message including thecounter value from the receiving node to the transmitting node whenpackets with said test bit set to zero have been received for apre-determined period of time.
 5. The method according to claim 1,wherein the step of comparing the counters after the pre-determinedperiod of time has ended is done manually.
 6. The method according toclaim 2, wherein said receiving node is arranged to forward the receivedpackets to still another node, wherein the method further comprises thestep of setting said received test bit to zero before forwarding thepacket to said still another node.
 7. The method according to claim 1,wherein said packet mode communication network is an intermediarytransmission network comprising several nodes provided with counters andwherein said two pre-determined nodes are two endpoints on either sideof the intermediary transmission network, wherein the method furthercomprises the step of deactivating the counters at the intermediarynodes between the two endpoints.
 8. An arrangement for measuring atransmission quality in terms of lost packets between two pre-determinednodes arranged to transmit and receive packets in a packet modecommunication network, said arrangement comprising: a counter in eachnode arranged to count transmitted packets in one node and receivedpackets in the other node during a pre-determined period of time,wherein each node is arranged to be able to reset the counter on theother node; and, means for comparing the counters after thepre-determined period of time has ended in order to obtain a packet lossmeasurement.
 9. The arrangement according to claim 8, wherein thearrangement further comprises: means for setting a test bit in eachtransmitted packet in order to indicate to the receiving node that thepacket has been counted in the transmitting node, whereby the receivingnode increases the counter for each received packet where said test bitis set; and, means for setting said test bit to zero after thepre-determined period of time has ended in order to indicate to thereceiving node that the received packet not has been counted on thetransmitting node.
 10. The arrangement according to claim 8, wherein thearrangement further comprises means for fetching the counter value fromthe receiving node to the transmitting node.
 11. The arrangementaccording to claim 9, wherein the arrangement further comprises meansfor sending a message including the counter value from the receivingnode to the transmitting node when packets with said test bit set tozero have been received for a pre-determined period of time.
 12. Thearrangement according to claim 8, wherein the arrangement furthercomprises means for manually comparing the counters after thepre-determined period of time has ended.
 13. The arrangement accordingto claim 9, wherein said receiving node is arranged to forward thereceived packets to still another node, wherein the arrangement furthercomprises means for setting said received test bit to zero beforeforwarding the packet to said another node.
 14. The arrangementaccording to claim 8, wherein said packet mode communication network isan intermediary transmission network comprising several nodes providedwith counters and wherein said two pre-determined nodes are twoendpoints on either side of the intermediary transmission network,wherein the arrangement further comprises means for deactivating thecounters at the intermediary nodes between the two endpoints.
 15. Thearrangement according to claim 8, wherein said packet mode communicationnetwork is an intermediary transmission network operated with anInternet Protocol (IP).
 16. The arrangement according to claim 8,wherein said packet mode communication network is an intermediarytransmission network on the Gb-interface connecting a GSM/EDGE RadioAccess Network (GERAN) to a core network (CN), wherein said twopre-determined nodes are a Base Station System (BSS) and a Serving GPRSSupport Node (SGSN).
 17. The arrangement according to claim 8, whereinsaid packet mode communication network is an intermediary transmissionnetwork on the Abis-interface connecting a Base Station Controller (BSC)with at least one Base Transciever Station (BTS), wherein said twopre-determined nodes are said Base Station Controller (BSC) and saidBase Transciever Station (BTS).
 18. The arrangement according to claim8, wherein said packet mode communication network is an intermediarytransmission network on the Iu-interface connecting a UniversalTerrestrial Radio Access Network (UTRAN) to a core network (CN), whereinsaid two pre-determined nodes are a Radio Network Controller (RNC) and aServing GPRS Support Node (SGSN).
 19. The arrangement according to claim8, wherein said packet mode communication network is an intermediarytransmission network on the A-interface connecting a GSM/EDGE RadioAccess Network (GERAN) to a core network (CN), wherein said twopre-determined nodes are a Base Station System (BSS) and a MobileSwitching Center (MSC).